In the hand, the fingers are moved by flexor and extensor tendons arising from muscles in the forearm. Inspection of the flexor tendon mechanism reveals three main components: 1) the skeleton, including the bones and the articulations or joints between the bones; 2) a tunnel or pulley system for the tendon; and 3) the tendon itself.
In each finger, two flexor tendons work to flex the proximal and distal interphalangeal joints, namely the flexor digitorum superficialis and the flexor digitorum profundis respectively.
A fibrous sheath holds the flexors tendons in close proximity to the phalanges of each finger to ensure that their pull produces immediate movement at the interphalangeal joint. In the absence of such a fibrous sheath, the flexor tendons simply “bow-string” and fail to produce the desired joint motion.
The flexor tendon sheath is highly specialized tissue that is anchored to bone and forms a very smooth but tight fibrous tunnel around the flexor tendon. With the flexor tendon surrounded by this flexor tendon sheath, there is a measurable hydrostatic pressure within the substance of the tendon. The flexor tendon sheath is not a uniform fibrous tunnel, but rather, is made of identifiable segments. The individual segments that make up the flexor tendon sheath are referred to as pulleys because of the mechanical role they play: holding the tendons close to the bone; preventing “bow-stringing” of the tendons; and ultimately translating the flexor tendon pull into joint motion.
For decades, surgical repair of severed tendons in the region of the hand containing the flexor tendon and the flexor tendon sheath has proven challenging and, to date, the results of such repairs are usually less optimal. For example, there are many current suture techniques designed for allowing the severed tendon ends to heal to each other while restoring the tensile strength of a tendon. Evidence gathered in connection with these various suturing techniques suggests that the number of suture strands and/or material across a tendon repair site directly correlates with the strength of the repair. In most situations, even when handling the tendon with the most delicate surgical techniques, the repair site ends up bulky and irregular. Thus, in contrast with the smooth and compact tendon located at the distal and proximal ends of the repair, most repair sites resemble bulky, irregular knots.
Given that the average repair site is often bulky or knotted, the repair site tends to abut the edges of the pulleys in the flexor tendon sheath, interfering with the tendon's ability to glide through its respective tendon sheath. Moreover, because the opening of a pulley does not expand to accommodate the bulk of the repair site, the edge of the pulley will often inflict significant damage to the repair site with every pass through the pulley, thereby impeding the tendon's ability to heal and adversely affecting the patient's overall post-operative recovery.
Repetitive injury to the repair site from the edge of a pulley may also contribute to the development of a “gap” across the repair site. Said “gap” consists of a premature separation of the sutured tendon edges, while the suture itself is still in continuity. Clinically, at this stage it may not be apparent that a rupture is imminent because the sutures are still holding. Nevertheless, the formation of a “gap” in the repair site will severely compromise the healing or it may simply make it impossible for the tendons to heal to each other. As a result, the suture eventually ruptures, at which point it becomes clinically evident that the repair has failed. In addition, rupture of the tendon repair can be caused by a combination of poor gliding of a bulky repair site and sufficient pull on the tendon during rehabilitation, or from patients who prematurely resume forceful activity that may exert a force in excess to what the repair site can withstand. Overly aggressive rehabilitation after flexor tendon repair surgery—which is intended to minimize stiffness—may also result in increased rated of tendon rupture.
Yet another very common and significant problem associated with tendon repair is the development of fibrosis and adhesions around the tendon and the repair site. Adhesions and fibrosis between the tendon repair site and the surrounding tissue is fostered by poor tendon gliding within the flexor tendon sheath during the healing process and results in finger stiffness and poor function. A second surgery referred to as “flexor tendon tenolysis” may be necessary to release the adhesions and fibrosis in order to improve finger motion. Tenolysis surgery is performed months after the original tendon repair surgery and is very demanding. Unfortunately, the results after tenolysis surgery are only moderately successful at best. Thus, patients who have had flexor tendon repair surgery face potentially significant complications either in the form of finger stiffness or tendon rupture before healing has occurred.
Yet another dilemma encountered in flexor tendon repair surgery is the tendency of an end of a flexor tendon to become inflamed and/or engorged after it has been severed, thereby making it difficult for the surgeon to direct and manipulate the tendon end through the flexor tendon sheath to a desired location. The situation is analogous to feeding the end of a frayed rope through the mouth of a pipe—only incalculably more delicate. Moreover, once the surgeon is able to direct the tendon end to a desired location, one or more inflamed and/or engorged severed tendon ends may further exacerbate the bulkiness and/or knottiness of the resulting repair site.
These, as well as other complex problems often associated with tendon repair, have led many surgeons to recognize flexor tendon repair surgery as one of the most difficult and challenging forms of surgery in the hand. Indeed, the surgical community often refers to the region of the hand containing the flexor tendons as “no man's land.”
Accordingly, there is an existing demand for new and innovative flexor tendon repair techniques that will assist surgeons with, for example, facilitating the ability of a repair to glide through a flexor tendon sheath, while minimizing the amount of damage to the tendon that may be caused by excessive handling of the tendon during surgery when attempting to tunnel the cut end of a tendon through the pulleys of the flexor tendon sheath.
Several attempts have been made to help correct some of the problems associated with flexor tendon repair surgery. For example, U.S. Pat. Nos. 5,897,591 and 3,842,441 both disclose a temporary tubular implant which prevents the formation of post-operative fibrous adhesions between a repair site and its surrounding tissue. Furthermore, U.S. Pat. No. 7,112,221 discloses an implant which can be strapped around a bone, thus providing a prosthetic support which supplements the tendon sheath.
These and other references, however, do not address the problems that a surgeon often encounters when a repair site and/or tendon end is too bulky or inflamed to smoothly enter into one or more of the various pulleys in the flexor tendon sheath. Therefore, a device and method are desired that will assist a surgeon in directing a severed tendon end through the pulley system of its respective flexor tendon sheath to a desired location. More importantly, a device and method are desired that will facilitate the smooth gliding or passage of a repair site through its corresponding pulley system during tendon healing.